1. Field of the Invention
The present invention generally relates to liquid infusion systems. More particularly, the present invention relates to a sealing arrangement for a fluid reservoir of an infusion pump. The sealing arrangement provides increased reliability in the seal between the components of the infusion pump creating the fluid reservoir.
2. Description of the Related Art
Frequently in the healthcare field, it is desirable to provide a patient with a solution, medicine, drug, or other substance, on a continuous basis for a period of time. For example, after a surgical procedure, it may be desirable to administer a liquid pain medication to the patient at a controlled rate, over a significant amount of time. In such situations, it may be desirable that this be accomplished while the patient is in an ambulatory state. A variety of portable infusion devices have been developed to accomplish this purpose.
One common portable infusion device is referred to as an elastomeric infusion pump. An elastomeric infusion pump typically utilizes one or more elastic sleeves mounted over a cylindrical support member. The elastic sleeve is sealed to the support member at both ends and a drug, or other substance to be infused, is introduced into a space, or reservoir, between the sleeve and the support member. As the infusion pump is being loaded with the drug, the elastic sleeve expands in a generally radial direction about the support member. While in an expanded condition, the elastic sleeve exerts a pressure on the drug, which forces the drug through an outlet of the elastomeric pump. A delivery device, such as a catheter, is in fluid communication with the elastomeric pump to deliver the pressurized drug to the patient.
Importantly, a secure seal must be created and maintained between the elastic sleeve and the support member to ensure proper and reliable operation of the elastomeric pump. An annular member, or O-ring, made from an elastic material, is often used to create a seal between the elastic sleeve and the support member. Under ideal conditions, a properly sized and installed O-ring may exert a sufficient force on the elastic sleeve to create and maintain a seal between the sleeve and the support member. However, elastic, O-ring type sealing members possess certain disadvantages, making them less than ideal under actual use conditions.
For example, an O-ring sealing member relies on inherent elasticity to be capable of increasing from its nominal diameter, in order to be assembled onto the combination of the support member and sleeve. Further, the O-ring relies on inherent elasticity to return toward its nominal diameter and, thus, apply a sealing force to the elastic sleeve. Accordingly, physical properties and dimensions of the O-ring sealing member influence the predictability and reliability of the seal.
However, due to normal manufacturing variations, certain physical dimensions of an O-ring sealing member, such as the inner diameter, may vary significantly from a desired, nominal value. Such variations may result in the O-ring, if the inner diameter is significantly smaller than the nominal value, being difficult to assemble over the elastic sleeve and support member. Conversely, if the inner diameter is too large, the O-ring may not exert a sufficient force on the elastic sleeve to create a secure seal between the sleeve and the support member.
Furthermore, common materials used to produce O-rings having a desirable amount of elasticity tend to have a relatively soft outer surface and may be easily damaged during handling, assembly and normal usage. Surface damage to an O-ring type sealing member, such as small cuts or tears, may result in failure of the O-ring and resulting failure of the elastomeric pump. In addition, imperfections in the raw material or the manufacturing process may result in premature failure of the O-ring.